Paperboard corrugating medium treatment



Sept. 10, 1963 D. E. KANE PAPERBOARD CORRUGATING MEDIUM TREATMENT Filed Dec. 16, I959 Wm NM mm km mm INVENTOR. Daniel E. Kane BY 2% PW Attorneys United States Patent Fibreboard Calif., is

This invention relates to the treatment of a paperboard co-rrugating medium web, and more particularly to treatment of such web with polyethylene of an emulsifiable type to increase runnability of the web through the usual corrugating rolls while simultaneously minimizing fracture or rupture of the web which may otherwise occur from the corrugating operation.

The paperboard web which is corrugated for the manufacture of corrugated paperboard is known in the industry as the corrugating medium. In corrugating the web, it is run through conventional fluted corrugating rolls. Heretofore, there has been a problem in corrugating the web by the rolls without rupturing or fracturing the same, particularly at relatively high speed. Fracturing results in weakening of the corrugating medium; and this impairs the strength of the ultimate corrugated paperboard which is made by a-dhesively securing plane sheets of paperboard to the ridges of the corrugating medium. In an etlort to overcome this problem, it has been proposed to treat the corrugating medium before it is corrugated by the corrugating rolls, with various types of lubricants such 'as lubricating oil, Wax, lOI' asphalt, or to apply such lubricant directly to the corrugating rolls as the web is being corrugated. Lubricants of this type have not been all that could be desired because fracturing or rupturing of the medium was not entirely eliminated, particularly at relatively high speeds of operation of the corrugating rolls, thus increasing production costs.

Summarizing the instant invention, it has as its object, among others, the provision of a simple and economical method embodying application of a particular well known type of polyethylene for enhancing runnability of a paperboard corrugating medium through conventional corrugating rolls while simultaneously minimizing fracture or rupture of the medium. The polyethylene is of an emulsifiable type which is applied to at least one surface of the corrugating medium web. It may be applied to the Web as a liquid composition, either as an aqueous emulsion or in -a solvent carrier, by any suitable mode of application such as by spraying but desirably by liquid coating application; or the web may be continuously moved over a solid slab or block of the emulsifiable polyethylene.

In one mode of application when the polyethylene is applied to the web in a paper manufacturing apparatus and subsequently wound up in a roll which may be stored prior to corrugating the web, it has been found advantageous to apply the emulsifiable type polyethylene to the web while it is still warm. The corrugating medium roll may then be stored for an indefinite time; and may be later corrugated by the corrugating rolls.

If the corrugating medium web has not been thus treated in the paper manufacturing apparatus, advantageous results have been obtained by continuously running at least one surface of the web over a solid block or slab of the emulsifiab-le type polyethylene, and desirably, both surfaces are thus treated. This is advantageously done as the corrugating medium is unwound from a roll, and the unwound web is being continuously fed to the corrugat-ing rolls.

Relatively small amounts of the emulsifiable type polyethylene applied over substantially the entire area of at least one surface of the web, have been found to minimize fracturing or rupturing of the corrugating medium 2 while simultaneously allowing increase of operating speed of the corrugating rolls from the usual running speeds of the web of 300 to 400 feet per minute, up to about 650 feet per minute, and even higher.

For a more detailed description of the invention, reference will be subsequently made to the accompanying drawings, in which,

F IG. 1 is a schematic fragmentary side elevational view of a conventional paper manufacturing apparatus having means therein for applying to the corrugating medium an aqueous emulsion of the emulsifiable type polyethylene;

FIG. 2 is a similar enlarged view of the portion of the apparatus encircled by line 2-.2 in 'FIG. 1, illustrating the emulsion applying means;

FIG. 3 is .a schematic fragmentary side elevational view illustrating a mode of application of the emulsifiable type polyethylene by means of slabs thereof just prior to the running of the corrugating medium web through conventional corrugating rolls.

Emulsifiable types of polyethylene are well known. They are partly oxidized and have in their carbon to carbon chain a certain number of oxygen-containing groups, mainly, carbonyl groups, such as ketonic, aldehydic, or carboxylic groups. They may be obtained by heating polyethylene while agitating and working the same simultaneously in the presence of an oxidizing medium, thus exposing uniformly the polyethylene mass to the oxidizing medium. Preferably, this is accomplished by hotmilling polyethylene in the presence of oxygen or any other suitable oxidizing agent.

Certain changes in the physical and chemical characteristics of the polyethylene occur during the oxidizing treatment. If the oxidizing treatment is mild, the polyethylene changes in white color to off white. Under higher temperatures and longer reaction time, the color will change to yellow, brown or even black, and a rancid odor may develop. 'For example, heating polyethylene for three or four hours in the presence of air at about C. results in lowering of its molecular weight because of chain breaking. Then increase in viscosity and molecular weight occur and also softening point, as a result of cross-linking by \oxygen. Continued oxidation, particularly at increased temperatures, causes degradation of the compound with liberation of volatile components such as water, fatty acids and carbon dioxide, and the formation of a brittle, wax-like product. Conventional ti-oxidents may be employed during the oxidizing heat treatment in order to prevent degradation.

By controlling reaction conditions of the polyethylene oxidation, it is thus possible to obtain a variety of products of a carbonyl oxygen concentration, which as carbonyl concentration increases causes gradiently increase in acid number. The particular emulsified types of oxidized polyethylene advantageously employed herein are those having an average molecular weight of about 1,000 to 25,000, desirably about 1,500 to 3,500; an acid number of about 4 to 20 which is a measure of the carbonyl oxygen content, desirably about 5 to 17; and a softening point of about 210 to 227 F. (ring I and ball, ASTM D-36-26). Any well known type of emul-sifiable polyethylene may be employed, but those which have been found most advantageous are Epolene E by Eastman Chemical Products, Inc., and A-C 629 by Semet-Solvay Petro-Chemical Division of Allied Chemical & Dye Corporation. Epolene E has an average molecular weight of about 2,500 to 3,000, an acid number of about 7 to 13, and a softening point of about 215 F., while A-C 629 has an average molecular weight of about 2,000 to 2,500, an acid number of about 14 to 17, and a softening point of about 217 F.

The employment of an emulsifiable type polyethylene has been found very important as polyethylenes of a non-emulsifiable type do not produce the desired results in increasing the speed of operation, namely, runnability, through the corrugating rolls while simultaneously minimizing fracturing or rupturing of the corrugating medium. Treatment with the emulsifiable polyethylene may be employed, as previously mentioned, either by applying the polyethylene as a liquid composition to the corrugating medium web, or by continuously moving the web in frictional engagement with a block or slab of the polyethylene. If the treatment is applied in the paper manufacturing apparatus, it is desirable to apply the polyethylene to the moving web in the form of a liquid composition, desirably as an aqueous emulsion, at any suitable location while the web is still warm and prior to winding the web in a roll. Under such circumstances, satisfastory results are obtained when the aqueous polyethylene emulsion at room temperature is applied to only one surface of the web because when the web is subsequently wound in a roll at the end of the paper manufacturing operation, some of the polyethylene on the treated surface of the web will transfer to the untreated surface because cf contact between the treated and untreated surfaces in the roll. This in effect provides a coating on both surfaces of the web when the roll thereof is formed at the end of the paper manufacturing operation.

It is desirable to apply the aqueous polyethylene emulsion to the web while the web is warm rather than when the paper is at an ambient temperature because the heat of the paper drives off water from the emulsion, thus minimizing penetration of the polyethylene into the body of the web. However, the polyethylene emulsion may be applied to the web while the web is at ambient temperature but then more emulsion would have to be applied because of water absorption.

Any suitable aqueous emulsion of the emulsifiable type polyethylene may be employed for this purpose, the proportions of the ingredients not being particularly critical. A typical emulsion is as follows in parts by Weight:

A-C 629 4-0 Oleic acid 8 Morpholine (tetrahydro-l,4,2H-oxazine) 8 Water 184 In the above example, the oleic acid and morpholine serve as emulsifying agents but any other suitable emulsifying agent may be employed such as those of the amine type, fatty acids and sodium and potassium soaps.

The emulsion may be formed in any well known manner, such as by heating the morpholine and water at a temperature of about 200 F., and then adding to the morpholine and water a molten mixture of the oleic acid and the emulsifiable type polyethylene at a temperature of about 212 F. to 230 F. and with vigorous agitation.

The above typical formulation has a solids polyethylene content of about 16% percent but after the emulsion is formed, it is preferably diluted further with water to about a 1 percent polyethylene concentration but this is not critical. Very small amounts of the polyethylene will produce markedly improved runnability when the corrugating medium is subsequently run through the corrugating rolls. As little as 0.0030 pound of the polyethylene applied per 1,000 square feet uniformly over the entire area of the Web has provided marked improvement. The maximum amount is immaterial, being governed only by economical factors. Sufficient of the emulsion applied to the web to provide about 0.0068 pound of the polyethylene per thousand square feet uniformly over the surface thereof has been found desirable in commercial application. However, as previously r lated, this is not critical as more or less can be applied.

Instead of applying the emulsifiable type polyethylene 4,. in emulsion form, it may be applied by solvent deposition such as by dissolving the polyethylene in any suitable solvent such as naphtha or carbon tetrachloride. However, solvent deposition is messy and is not as desirable.

A desirable manner of applying the emulsion of the polyethylene in the paper manufacturing operation is il lustrated in FEGS. 1 and 2. Referring to- FIG. 1, a conventional Fourdrinier paper making machine is illustrated at 2, the paper pulp being fed on (to the Fourdrinier screen 3 from head box 4. Such machine includes conventional screen supporting rolls 6 and suction boxes 7. After leaving couch roll 8, the web 9 which is still moist is passed through conventional press rolls 10 from which it continuously moves through conventional groups of dryer rolls 1-11 (only a few of which are shown).

Usually a conventional so-called size press 12 is provided in the apparatus for applying various types of size coatings to the web if such coatings are desired. This size press is employed for applying the polyethylene emulsion hereof. It comprises a driven rubber covered pickup roll 13 which extends at least the width of the web and transfers the emulsion from a so-oalled water box 14 to a smooth driven metal applicator roll 16, both of which also extend at least substantially the full width of the web. Water box 14 is open at its side adjacent pick-up roll 13, so that the emulsion contacts the rubber cover on the roll; and applicator roll 16 applies the emulsion across the entire surface of the underside of the moving web.

The emulsion is continuously fed into water box 14 from a supply tank 17 by a pump 18 connected by piping 19 to an emulsion feed manifold 21 extending widthwise of the water box and to which are connected a plurality of spaced apart discharge spouts 22. Excess emulsion continuously flows by gravity from the water box through piping 23 to tank 17. Make-up stock is supplied to the tank 17 from time to time as conditions require; and the amount of emulsion applied is governed by control of the speed of operation of pump 18.

From size press 12, the web passes through another group of dryer rolls 24 from which it continuously passes through the usual calender rolls (not shown), and is then wound into a roll which is slitted into desired widths by conventional slitter and rewinder mechanism (not shown). The thus treated corrugating. medium roll can be then stored, and later shipped to the place where it is to be corrugated by conventional fluted corrugating rolls of the type shown at 31 in FIG. 3. At the size press, the selfsupporting web of paper is still warm, varying in temperature from F. to F. but as pointed out above, the temperature is not critical.

If the emulsifiable type polyethylene is not applied in the course of manufacture of the paper, it may be applied to an untreated web of the paper while it is at room or in other words ambient temperature, just after the paper is being run off a roll thereof to the corrugating rolls. In such application, it is not desirable to apply the polyethylene in emulsion or other liquid form because the paper being cool there is more absorption of the liquid inasmuch as cool paper does not drive off the liquid. Under such circumstances, it is desirable to apply the polyethylene to both surfaces of paper by running the same over blocks or slabs of solid polyethylene of the emulsifiable type.

FIG. 3 illustrates such mode of application. The corrugating machine is of conventional construction including rotatable and opposed corrugating rolls 31 which are steam heated to a temperature of about 320 F. and which usually vary in diameter from 6 to 16 inches but the diameter of the rolls is not cnitical. Associated with the corrugating rolls 3 1 is a liner feed roll 32 which continuously supplies a paperboard liner 33 from a roll 34 thereof to a face of the corrugated corrugating medium 36 to which adhesive has been applied. For applying the ad hesive to the corrugating medium a conventional adhesive applicator 37 is employed containing a suitable adhesive 38; the adhesive being transferred to a face of the corrugating medium by means of applicator roll 39.

Ahead of the corrugating rolls 31 is a conventional steam heated preheating roll 41 which heats the corrugating medium prior to the corrugating operation as heated paper corrugates easier; fixed guide rolls 42 being assooiat d with the preheater roll 41. In commercial practice, the preheater roll 41 is maintained at a temperature of about 300 F.

Treatment of both surfaces of the corrugating medium web with blocks or slabs of solid polyethylene can be effected by any suit-able means as the corrugating medium is continuously unwound from a roll 44 thereof. As is conventional practice, the web 45 as unwound from roll 44 passes over a spring mounted so-called dancer roll 46 carried by a frame 47. A pair of spaced apart lower arms 48 (only one of which is shown) is pivoted to frame 47 and the web passes between these arms; stop means 51 being provided to position the arms 48. These arms carry a suitable holder 52 extending transversely at least the full width of the web and on which a slab 53 of the emulsifiable type polyethylene is supported. The slab also extends at least the full width of the web.

Upper spaced apart arms 54 are also pivoted to frame 47 and carry a holder 56 which supports a slab 57 of the emulsifiable type polyethylene contacting the upper surface of the web at least the full width thereof. Arms 54 float and are gravity loaded by suitable application of weights to maintain contact of the polyethylene slabs with the surfaces of the web. A suitable loading of the floating arms 54 is about 1 pound for each inch web width. Thus, as the web passes between the polyethylene slabs 53 and 57, polyethylene rubs off onto both surfaces of the web by virtue of frictional engagement therewith.

In connection with the above described mode of application, both surfaces of the web are desirably treated because there can be no transfer from one surface of the paper to the other as it is not wound into a roll prior to the corrugating operation. A lesser amount need be applied by the slab treatment because of minimum penetration into the paper. Such an amount may vary from about 0.0006 to 0.0018 pound per thousand square feet of the paper uniformly over each surface thereof. A desirable amount is about 0.0010 pound per 1,000 square feet of surface but as before the amounts are not critical. The amount may be readily regulated by adjusting the loading of arms 54.

The caliper of the corrugating medium is relatively immaterial insofar as the amount of polyethylene applied is concerned and may vary in usual thickness from about 7 to 12 points, namely, about 0.007 to 0.012 of an inch which are conventional calipers for the corrugating medium. Irrespective of how the emulsifiable type polyethylene is applied, whether as a liquid composition or in solid form, the corrugating medium treated with the same can be corrugated at markedly increased speeds compared to prior speeds, with substantially complete elimination of fracturing.

I claim:

1. The method of enhancing the runnability of a paperboard corrugating medium web through corrugating rolls while simultaneously minimizing fracture of said web which comprises thinly applying to at least one surface of said web an emulsifiable polyethylene having an average molecular weight ranging between approximately 1,000 and 25,000, an acid number ranging between about 4 and 20, and a softening point ranging between about 210 F. and 227 F. and corrugating said web by passing it between opposed corrugating rolls.

2. The method of enhancing the r-unnability of a paperboard corrugating medium web through corrugating rolls while simultaneously minimizing fracture of said web which comprises thinly applying over substantially the entire area of at least one surface of said web an emulsifiable polyethylene having an average molecular weight ranging between approximately 1,000 and 25,000, an acid number ranging between about 4 and 20, and a softening point ranging between about 210 F. and 227 F. and corrugating said web by passing it between opposed corrugating rolls.

3. The method of enhancing the runnability-of a paperboard c-orrugating medium web through corrugating rolls while simultaneously minimizing fracture of said web which comprises thinly applying to at least one surface of said web while in warm condition a liquid composition containing an emulsifiable polyethylene having an average molecular weight ranging between approximately 1,000 and 25,000, an acid number ranging between about 4 and 20, and a softening point ranging between about 210 F. and 227 F. and corrugating said web by passing it between opposed corrugating rolls.

4. The method of enhancing the runnability of a paperboard corrugating medium web through corrugating rolls while simultaneously minimizing fracture of said web which comprises thinly applying over substantially the entire area of at least one surface of said web while it is moving through a paper manufacturing apparatus and it is still warm an aqueous emulsion of an emulsifiable polyethylene having an average molecular weight ranging between approximately 1,000 and 25,000, an acid number ranging between about 4 .and 20, and a softening point ranging between about 210 F. and 227 F. and corrugating said web by passing it between opposed corrugating rolls.

5. The method of enhancing the runnability of a paperboard co-rrugating medium web through corrugating rolls while simultaneously minimizing fracture of said web which comprises thinly applying to at least one surface of said web an emulsifiable polyethylene having an average molecular weight ranging between approximately 1,000 and 25,000, an acid number ranging between about 4 and 20, and a softening point ranging between about 210 F. and 227 F. by continuously moving said web surface in contact with a slab of the polyethylene and corrugating said web by passing it between opposed corrugating rolls.

6. The method of enhancing the runnability of a paperboard corrugating medium web through corrugating rolls while simultaneously minimizing fracture of said web which comprises thinly applying over substantially the entire area of each surface of said web while the web is at ambient temperature an emulsifiable polyethylene having an average molecular weight ranging between approximately 1,000 and 25,000, an acid number ranging between about 4 and 20, and a softening point ranging between about 210 F. and 227 F., by continuously moving each of said web surfaces in contact with a slab of the polyethylene and corrugating said web by passing it between opposed corrugatin-g rolls.

7. The method of enhancing the runnability of a paperboard corrugating medium web through corrugating rolls while simultaneously minimizing fracture of said web which comprises thinly applying over substantially the entire area of each surface of said web while the web is at ambient temperature an emulsifiable polyethylene having an average molecular weight ranging between approximately 1,000 and 25,000, an acid number ranging between about 4 land 20, and a softening point ranging between about 210 F. and 227 F., by continuously moving each of said web surfaces in contact with a slab of the polyethylene prior to corrugating said web, and corrugating said web by running it through opposed corrugating rolls.

References Cited in the file of this patent UNITED STATES PATENTS (Other references on following page) '7 UNITED STATES PATENTS Schoo Mar. 17, 1931 Shields June 12, 1951 Hunter Sept. 29, 1953 Doyle et a1. June 1, 1954 Segil Nov. 30, 1954 Erchak et a1 Oct. 9, 1956 Piscanchyn 'et a1 Feb. 17, 1959 Rosenbaum June 28, 1960 Little May 2, 1961 Shanley Feb. 12, 1963 

1. THE METHOD OF ENCHANCING THE RUNNABILITY OF A PAPERBOARD CORRUGATING MEDIUM WEB THROUGH CORRUGATING ROLLS WHILE SIMULTANEOUSLY MINIMIZING FRACTURE OF SAID WEB WHICH COMPRISES THINLY APPLYING TTO AT LEAST ONE SURFACE OF SAID WEEB AN EMULSIFIABLE POLYETHYLENE HAVING AN AVERAGE MOLECULAR WEIGHT RANGING BETWEEN APPROXIMATELY 1,000 AND 25,000, AN ACID NUMBER RANGING BETWEEN ABOUT 4 AND 20, AND A SOFTENING POINT RANGING BETWEEN ABOUT 210*F. AND 227*F. AND CORRUGATING SAID WEB BY PASSING IT BETWEEN OPPOSED CORRUGATING ROLLS. 